1. Field of the Invention
The present invention relates to an audio apparatus, and more particularly, to an audio apparatus suitable for karaoke.
2. Description of the Prior Art
Karaoke which was invented in the United States as "Music Minus One" for practicing classical symphonies and songs has remarkably been developed for singing popular songs for pleasure in Japan. With the development, karaoke not only is reimported to the United States but also is drastically spreading in various countries in Asia and Europe. In view of such spread, makers have been developing various functions for audio apparatuses for karaoke.
As an example of such an apparatus, a conventional audio apparatus will hereinafter be described. Referring to FIG. 1, there is shown a schematic block diagram of a relevant portion of the conventional audio apparatus. Reference numerals 1 and 2 represent a left input terminal and a right input terminal for receiving sound signals of the left and right channels from external apparatuses, respectively. Reference numerals 3 and 4 represent a left amplifier and a right amplifier which amplify sound signals received by the left and right input terminals 1 and 2.
Reference numeral 5 represents a microphone terminal for receiving vocal signals from a microphone 5a. The microphone terminal 5 is connected to a detecting circuit 6. Reference numeral 7 represents a control input terminal connected to a logical circuit 8. Reference numeral 9 represents a vocal canceling circuit.
Reference numeral 10 represents a switch controlled by a ternary control signal Sc outputted by the logical circuit 8. The switch 10 selects a terminal A and a terminal D when the signal Sc is of high voltage level (hereinafter, referred to as "H level"), selects a terminal B and a terminal E when the signal Sc is of middle voltage level (hereinafter, referred to as "M level") and selects a terminal C and a terminal F when the signal Sc is of low voltage level (hereinafter, referred to as "L level". Reference numerals 11 and 12 represent a left buffer circuit and a right buffer circuit. Reference numerals 13 and 14 represent a left output terminal and a right output terminal. Although not shown, for example, a signal from the microphone 5a and the left and right sound signals are transmitted by way of a mixing circuit and a power amplifier to a speaker to be outputted as sounds. Reference numeral 15 represents an order circuit controlled by operation buttons 15a, 15b and 15c.
An operation of the conventional audio apparatus thus structured will be described. To the left and right input terminals 1 and 2, stereo sound outputs of an apparatus such as a laser disk player, a compact disk player and a video cassette recorder are coupled.
The left and right sound signals are outputted as left and right signals Sl and Sr through the left and right amplifiers 3 and 4, respectively. The left signal Sl is coupled to the terminals A and F of the switch 10 and the right signal Sr is coupled to the terminals C and D. In addition, the signals Sl and Sr are transmitted to the vocal canceling circuit 9. The vocal canceling circuit 9 performs one-to-one subtraction of the signals Sl and Sr. The result is supplied to the terminals B and D of the switch 10 as an accompaniment signal Svc where the vocal of the singer recorded on a disk or a magnetic tape on the left and right channels in the same phase and amplitude is canceled.
In the normal music reproduction, the buttons 15a and 15b are not depressed and the control signal Sc is of H level. Thereby, the switch 10 is connected to the terminals A and D and the left and right sound signals merely pass the switch 10 and are supplied from the left and right output terminals 13 and 14 through the buffer circuits 11 and 12, respectively.
When the user enjoys karaoke with this apparatus, the following two cases are dealt with: a first case where so-called "sound multiple karaoke" is reproduced; a second case where a sound source other than karaoke is used as karaoke by canceling the vocal of the singer by using the vocal canceling circuit 9 so that only accompaniment signals are left.
In the first case, since only the accompaniment signals are recorded on the left channel and both the accompaniment signals and model vocal signals are recorded on the right channel, the user depresses the button 15a so that his or her selection is transmitted to the logical circuit 8 by the order circuit 15. Consequently, the control signal Sc is of L level so that the switch 10 selects the terminals A and F. As a result, only the accompaniment signals are outputted from the left and right output terminals 13 and 14 through the left and right buffer circuits 11 and 12. Hereinafter, this case will be referred to as "sound multiple mode".
In the second case, the button 15b is depressed and the control signal Sc is of M level, so that the switch 10 selects the terminals B and E. As a result, the accompaniment signal Svc is outputted from the left and right output terminals 13 and 14 through the left and right buffer circuits 11 and 12. Hereinafter, this case will be referred to as "vocal canceling mode".
The above-described are cases where the user enjoys reproduced music and karaoke in the normal manner. As an additional function, a function called "vocal assisting mode" is provided. According to this function, when the user who is singing to karaoke forgets the words and cannot sing any more, vocal signals from the sound source are outputted together with the accompaniment signals.
Specifically, the detecting circuit 6 detects that the level of the input from the microphone 5a becomes a predetermined level or below and outputs a detection signal Sd. The detection signal Sd is transmitted to the logical circuit 8 and when the button 15c representative of the vocal assisting mode is depressed, forcibly switches the level of the control signal Sc to low in the sound multiple mode and to high in the vocal canceling mode.
Thereby, music including the vocal of the singer is outputted from the left and right output terminals 13 and 14 at a pause of the sound from the microphone 5a.
With the above-described conventional arrangement, however, the vocal assisting mode cannot be employed for a sound source called "reverse sound multiple karaoke" which is one of the karaoke sound sources on the market. In this sound source, reversely to the above-described sound multiple karaoke, only the accompaniment is recorded on the right channel and both the accompaniment and model vocal are recorded on the left channel.
Even if it is possible for the user to reverse the connection of the left and right input terminals 1 and 2 in some form to enjoy the reverse sound multiple karaoke, it is very inconvenient to change the connection of the terminals for each karaoke sound source.